The purpose of the work is to determine the pathway and regulation of AMP catabolism in several prokaryotic and simple eukaryotic organisms. Experiments will attempt to identify the rate limiting enzyme of AMP degradation in E. coli, Salmonella, Rhodospirillum and Baker's yeast. One of the enzymes will be purified and its regulatory properties will be characterized.. In vivo metabolic experiments with Azotobacter vinelandii will correlate the changes in intracellular ATP, AMP and Pi with changes in the activity of AMP nucleosidase. From these experiments it should be possible to demonstrate a corresponding increase of AMP nucleosidase activity with a decrease in adenylate pool size. BIBLIOGRAPHIC REFERENCES: The Pathway of Adenylate Catabolism in Azotobacter vinelandii. Evidence for Adenosine Monophosphate Nucleosidase as the Regulatory Enzyme V. L. Schramm and F. C. Lazorik J. Biol. Chem. 250, 1801, 1975 (Submitted with this report).